Air operated hoist

ABSTRACT

A hoist has a series of spaced guide pulleys that define a helical path for a cable passed over the pulleys. A ram cylinder is equipped with a piston that moves in an axis coaxial with the axis of said helical path, and means are provided so that movement of the piston separates said pulleys to lengthen the helical path so as to move the cable to lift a load. The pulleys and ram are within a casing, and an internal surface of the casing coacts with extensions of the piston to guide and reinforce the piston for movement in the cylinder.

United States Patent [56] References Cited UNITED STATES PATENTS 11/1882Butz..... 3,304,061 2/1967 Seward.........................

[72] Inventor JamesOrr Birmingham, Mich. 816,361

[2l] Appl. No. [22] Filed Apr. l5, 1969 [45] Patented Jan. 19, 1971 168,184; 248/328; 242/54 force the piston for movement in the cylinder.

PATENEDJAmslsn 3555435 SHEET 1 F 5 INVENTOR.

JAMES O/P? BY ATTORNEYS PATENTEU JAM 91971 SHEET 2 UF 5 Vfl/lfm l SHEEY3 UF 5 PATENTED JAN 1 9. Isn

AIR OPERATED I-IOIST This invention relates to a hoist, and moreparticularly a hoist of that class in which a part of a cable is woundover a series of spaced guides such as grooved pulleys, means beingprovided for moving the pulleys in directions away from one another, themovements of the pulleys naturally lengthening that part of the cablethat is applied to the pulleys, and there fore bringing about thelifting of a load that is attached to one end of the cable.

A hoist of the particular class is well shown in the Platz U.S. Pat. No.2,613,903 issued Oct. I4, 1952, where linearly spaced pulleys areadapted to be moved relatively to one another to bring about liftingmovement of a load attached to a hook on yone end of a cable applied tothe pulleys. The construction of the Platz patent is particularlyadapted for use in a balancing hoist. Thus, the maintenance ofpredetermined air pressure against the piston of the ram that is foundin Platz, is adapted to balance the load, once it is elevated, so that avery light pressure on the load in one direction or the other will beeffective to move the load. This is all well set forth in the Platzpatent and other prior art patents disclosing balancing hoists.

'Ihe invention that I have conceived, while also adapted particularlyfor use in a load-balancing hoist, is also useful in a hoist of theclass in which it is merely desired to lift and lower a load and to holdthe load in any lifted position.

My invention and its contribution can be best understood afterconsidering what has been done by the prior art. The earlier hoists ofthis class, of which Platz is an example, generally utilize a pistonthat is relatively small in diameter as rather considerable throw isnecessary to move the guide pulleys to contribute required lift to theload. By requiring a greater volume of air, a larger piston wouldnaturally act toov slowly. Also, the pulley arrangement found in theprior art places considerable stress on the cable, since they requirethe cable to bend through a rather large angle, thereby shortening itslife and seriously affecting its reliability. Generally, also, theearlier arrangements require rather considerable head room because oftheir vertical dimension, and that head room is wasted since the loadcannot be lifted any higher than the lowermost portion of the frame ofthe hoist.

It is obvious further, that the relatively small piston area utilized inthe prior art requires high air pressure, if a heavy load is to belifted. Frequently, such high pressure is not available in an industrialplant.

ln my invention, I contribute a rather unique arrangement .of spacedpulleys, making possible the elimination of large angle bends in thecable, and therefore contributing long life to the cable that isrequired in the operation of the hoist.

As a further feature of my invention, I am able to utilize a ramcylinder ot' relatively large diameter, having a piston of veryconsiderable area. This means naturally, that even a low air pressurewill resolve itself into a rather considerable total pressure applied tothe piston. The piston of my ram then can act eectively through thecable guide pulleys to apply extremely high pressures to the hoistcable, so as to contribute swift and effective hoisting movement eventhough the air pressure is relatively low. The need for large areapistons was recognized earlier by the art, as can be seen by a review ofa Powell U.S. Pat. No. 3,260,508. However, no practical way of using alarge piston in an effective assembly has been contributed until thepresent time, so far as I know.

As a further feature of my invention, l mount the ram cylinder andpiston so that the axis of movement of the ram piston is parallel to theaxis of a helical path in which the cable lies, and in which the cableis guided by the several pulleys. It follows therefore, as will appearquite clearly from a viewing of the drawings of my invention, that myhoist requires a minimum of head room, thereby contributing greatly toits effectiveness and versatility.

Of course, as will be emphasized presently, my hoist contributes thisfeature of low head room without requiring the hoist to be mounted in anoffset and unbalanced position. For an understanding of this feature,reference is made to the Platz considerable length of the beam on whichthey are mounted,

and the load is offset a considerable distance relatively to themounting of the hoist on the beam so as to exert tilting leverage. Aconsiderable tilting leverage, if a relatively heavy load is to belifted, presents a rather serious problem. In the hoist contributed byme, the mounting is exceedingly simple, and it is practical to supportthe hoist through means that are substantially in vertical alignmentwith the load secured to the load end of the cable.

As a still further feature of my invention, the large diameter pistonthat I use operates through cam mechanism to bring about the movement ofthe cable guides or pulleys. This cam mechanism contributes greatmechanical advantage to the piston of the ram cylinder, and makespossible the application of a high degree of lifting force andconsequent swift and effective movement of the load, with a betterbalancing of the load while utilizing relatively low air pressureexerted against the piston.

As a further feature of my invention I utilize a novel form of pistonand cylinder as well as a novel hoist casing for mounting the severalparts. Thus, my piston is naturally formed, in accordance with myconcept, with surfaces for moving the spaced pulleys. These surfacesextend from a skirt with which the piston is formed, and which travelsin the relatively short cylinder that I utilize with my piston of largesections. Because of the short cylinder I use, the guiding of the pistonin its movement becomes critical. I have conceived utilizing the casingin which my piston and cylinder are housed, for this purpose. Therefore,l form my piston with arms or the like extending axially therefrom,preferably from points between the surfaces of the piston that actuatethe spaced pulleys, and I provide surfaces on the casing of the hoistfor coacting with these arms to guide and support the piston.

l have thus outlined rather broadly the more important features of myinvention in order that the detailed description thereof that followsmay be better understood, and in order that my contribution to the artmay be better appreciated. There are, of course, additional features ofmy invention that will be described hereinafter and which will form thesubject of the claims appended hereto. Those skilled in the art willappreciate that the conception on which my disclosure is based mayreadily be utilized as a basis for the designing of other structures forcarrying out the several purposes of my invention.

Referring now to the drawings:

FIG. 1 shows a longitudinal section of a hoist embodying the inventionthat I have conceived.

FIG. 2 is a view similar to Fig. l, but showing parts in a loadliftingposition.

FIG. 3 shows a section taken along line 3-3 of FIG. l, with dash anddotted lines added to show a position of the several cable guides whenthe load is elevated.

FIG. 4 is an end view of the hoist looking in the direction of the arrow4 in FIG. l.

FIG. S shows a modification of my invention utilizing two pistons thatmove several groups of cable guide pulleys.

FIG. 6 is a view similar to FIG. 5, but shows the pulleys moved by thepistons into a position corresponding to the lifting of the load.

FIG. 7 is a section along line 7-7 of FIG. 5. Referring now moreparticularly to the drawings, and especially FIGS. l to 4', the casingof my hoist is designated by reference numeral l0. A part 1l is formedon casing 10 as an integral portion thereof, or is welded thereto. Partl1 is supported through a suitable bearing assembly 12 relatively to aplate 13 that is fastened to a trolley beam 14. The trolley beam 14 isin turn mounted through rollers 15 on a support beam 16. Through theparticular construction, the hoist casing 10 will rotate relatively tothe trolley beam 14, and may move with beam 14 on rollers 1S relativelyto the support beam 16. Of course, it will be appreciated that thecasing I may be supported in many ways, and conceivably, may be equippedwith a hook for suspension from a ceiling as those skilled in the artwill fully appreciate.

One end wall 20 of the hoist casing I0 is dished as shown in FIGS. I and2. At 21 there is an opening in wall 20 that is threaded for fitting 22attached to one end of an airhose 23. Obviously, air may flow underpressure into a ram cylinder pressure chamber P inwardly of wall 20whenever desired. My invention contributes a novel ram cylinder and avery unusual piston as I have earlier outlined. This piston is shownrather clearly in section in FIGS. l and 2, where it is designated byreference numeral 25. It will be seen that piston 25 has an inclined camsurface 26 against which operate a pair of rollers 27 that are rotatablymounted at one end of a pulley mounting member 23.

It will be appreciated, as is apparent from FIG. 3, that there are threeof these mounting members 28, and therefore three sets of rollers 27operating against three surfaces 26 formed on the piston 2S. Therefore,the three surfaces 26 of the piston 25 will be spaced 120 from oneanother, and that is why only one surface 26 is seen in FIGS. I and 2. Ihave purposely eliminated showing in FIGS. I and 2 the two additionalmounting members 28 that can be seen in FIG. 3, in order to simplify theshowing and to emphasize the construction of the piston 25. It will bewell to add that I may use four, five or more mounting members 28, and alike number of surfaces 26, altering then the cross section of thecasing I0 in a corresponding manner.

It will be noted that the piston 25 has a skirt portion 30 that iscircular, and which is formed so as to carry a piston ring 31, or somesuitable packing applied against surface 35 of the ram cylinder, thatwill make it possible for the piston 25 to move effectively upon theadmission of air pressure into the chamber P. In order to balance therelatively short piston 25 for effective movement, it is formed with aseries of arms 32, only one of which is naturally shown in FIGS. ll and2. All three amis are shown clearly in section in FIG. 3 The three arms32 rest against three surfaces S on the inside surface of casing Ril.

It will be seen also that the three arms 32 are spaced circumferentially120 apart, just as the cam surfaces 26 are spaced 120 apart, and thatthe arms 32 are positioned angularly between the surfaces 26 so as tobetter contribute balanced guidance to the piston 25. Actual contactbetween the arms 32 and the surfaces S is through ball bearing 32amounted on the arms 32 by suitable means.

In order to make even more clear the relationship of the parts in FIGS.I and 2, line x-x has been added to indicate the axis of the ramcylinder. It is clear that the piston 25 has its center on the line x-x,and that x-x is the centerline of the surface 35 of the ram cylinderrelatively to which the skirt 30 of the piston 25 and the packing 3lslide under the influence of air pressure in the chamber P. Lines Y andZ have been shown in FIGS. 2 and 3, further to clarify the relation ofthe surface 35 of the ram cylinder to the casing 10 and the surfaces Sthat coact with arms 32.

Each of the three mounting members 28 is formed symmetrically so that atits end opposed to that end on which the rol- Iers 27 are mounted, itcarries rollers 36 mounted exactly as are the rollers 27. Those rollers36 coact with three surfaces 37 formed on the inner surface of a cover38 that is secured to the end of the casing opposite the dished end wall20 of the casing. The three surfaces 37 are in exact alignment with thesurfaces 26 of the piston 25, and coact with the rollers 36 in exactlythe same manner that the rollers 27 coact with the surfaces 26 of thepiston 25. It is obvious from FIGS. E and 2 that endwise movement of thepiston 25 from its position of FIG. I to its position of FIG. 2 willbring about the camming movement of the particular mounting member 23shown in FIGS. I and 2 from the position of FIG. 1l to the position ofFIG. 2.

The movement of the three mounting members 28 is well illustrated alsoin FIG. 3. There, in full lines, parts of the three mounting members 28are shown in the position of FIG. 1. They are shown in dash and dottedlines in the position of FIG. 2.

I shall now describe the detailed construction of one of the mountingmembers 28, it being understood that the three mounting members areconstructed in a similar way and function in exactly the same manner tobring about a movement of the cable. As is evident from FIGS. 1 and 2,each mounting member includes a shaft 40 that extends between two endwalls 4l and 42. Also, l show end walls 4I, 42 connected by studs 62 andequipped with portions 43 and 44 on which the several rollers 27 and 36are mounted for rotation. The shaft 40 is preferably held in position onend wall 4l through a threaded construction 45, and mounted on shaft 40are a series of ball bearings 46, each ball bearing supporting forseparate rotation a guide member in the form of a pulley 47. The severalpulleys 47 will be maintained against contact from one another bybearings 46 while freely rotatable individually and independently on thesaid ball bearings 46. Each of the mounting members 28 does, of course,support its own group of the pulleys 47.

The arrangement of the several groups of pulleys on the several shafts40 carried by the several mounting members 28, is such that the outerguide surfaces of the pulleys will define a helical path for a cable 50that is applied to the pulleys, with the axis of the helix coincidingwith line x-x. As shown best in FIGA 3, one end of this cable is headedat 51, and through a suitable U-shaped yoke 52 is secured by a pin 53 toan integral portion 54 of the casing l0x From its headed end 51, thecable 50 will extend as probably best seen in FIG. 3, to the righthandlowermost end pulley 47 and then upwardly over the uppermost pulley andthen downwardly tothe left-hand lowermost pulley 47, and then around thenext right-hand pulley and so forth until it has passed over all of thepulleys desired. It then extends downwardly, as shown in dotted lines at50a, outwardly of the hoist casing through an opening 55 in the casingto a load hook 56.

I believe it will now be apparent that when the piston 25 is moved fromits position of FIG. 1 to its position of FIG. 2, the guide pulleys 47will move in a direction away from the axis of casing l0. Thus, theseveral groups of pulleys 47 will have relative separating movementsfrom the full line position of FIG. 3 to the dash and' dotted lineposition of FIG. 3. This will naturally increase the length of thehelical path defined by the pulleys 47, and will increase the length ofthe cable occupying that path, thereby bringing about the lifting of thehook 56 and a load attached thereto.

Of course, should balancing control be applied to air pressure actingthrough hose 23 against the piston 25, the load on hook 56 will be heldbalanced so that that load may be manipulated as set forth in the priorart patents to which I have referred. However, it will also beappreciated that the hoist that I have described will operateeffectively without the balancing feature, merely through theapplication of pressure to the piston 25, and the holding of the piston25 under pressure in a particular elevated position of the load. Whensimply used for lifting purposes, my hoist can operate with considerablespeed so as to lift a load swiftly.

In order to hold the cable 50 on the several guide pulleys 47, each ofthe mountingI members 28 is equipped witha cover 60, best shown in FIG.3, is preferably formed of metal, and has a pair of eyes 61 which areheld in place on the end plates 41 and 42 by the studs 62. In order notto complicate the showing, these studs are not illustrated in FIGS. land 2, 'but are well shown in section in FIG. 3. Of course, thoseskilled in the art will appreciate the means for effectively holding thecable in position may be otherwise formed, but I prefer the meansillustrated.

In FIGS. 5, 6 and 7, I show a modification of myhoist in which there areseveral mounting members each designated by reference numeral 70.Actually, there are six of the members 70 as will be clear from FIG. 7,certain of the members being omitted for reasons of clarity in FIGS. 5and 6. There is a group of individually mounted guide pulleys 71 on eachmember 70. A cable 72 is mounted in a helical path as determined by theseveral pulleys 7l, the nature of this helical path being indicated inFIGS. 5 and 6. Thus, it will be noted that the extreme left pulley 7l onthe bottom mounting member 70 of FIG. 5 is directly under a spacer 73 onthe upper mounting member 70. The bottom portion of the hoist casing mayhave a guide wheel 72a that lies in a plane to the left of the extremeleft pulley 71 on upper mounting member 70. The remaining pulleys,including those pulleys of the other mounting members in bothmodifications of my invention are similarly related and define what Iterm a helical path.

ln the modification of FIGS. 5, 6 and 7, instead of utilizing a singlepiston, I utilize a pair of pistons, one being designated by referencenumeral 74 and the other by reference numeral 75. The two pistonsoperate in a cylinder 76 formed with a center wall 77 having a passage78. The piston 75 has a threaded opening 79 to which is secured the endfitting 80 of an airhose 81. It is obvious that when air is admittedinto the cylinder 76, it will flow to each side of the central wall 77through the opening 78, and will bring about movement of the two pistons74, 75 from the position of FIG. 5 to the position of FIG. 6.

Each one of the six mounting members 70, in the modification of FIGS. 5,6 and 7, is formed with two cam surfaces, one of which is designated 85and the other 86. The piston 74 is formed with a series of arms 87having rollers 88 for cooperation with the several cam surfaces 85.Similarly, the piston 75 is formed with a series of arms 89 having aseries of rollers 90 that coact with the cam surfaces 86. Obviously,movement of the two pistons 74, 75 from the position of FIG. 5 to theposition of FIG. 6 will bring about the movement of the several mountingmembers 70 from the positionv of FIG. 5 to the position of FIG. 6. Thiswill act to lengthen the helical path of cable 72 for bringing about themovement of the cable and the lifting of a load L, FIG. 7, which may beattached by a hook 92 to the cable 72.

I claim:

l. ln a hoist of the class described, a load cable, a series of spacedcable guides movably mounted on said hoist and having guide surfacesover which said cable is applied, said guide surfaces definingtherebetween a helical path for said cable, a ram cylinder on said hoistpositioned with its piston moving in an axis traversing the spacedefined by said helical path and parallel to the longitudinal axis ofsaid helical path, and means whereby said piston moves at least certainof said guides transversely of the axis of said piston and said helicalpath to move said guides in directions away from one another whereby toeffect a lengthening of said helical path and increased winding of saidcable about said guides.

2. In the combination of claim l, the feature that said cable guides aremounted to rotate in axes that are parallel to the axis of said rampiston.

3. In the combination of claim 2, the feature that said cable guidescomprise a series of independently rotating grooved pulleys. l

4. In the combination of claim 3, the feature of cam means through whichsliding movement of said piston moves said grooved pulleys.

5. In the combination of claim l, the feature that said ram piston movesin the axis of said helical path, and cam means actuated by said pistonfor moving Isaid guides radially of said axis.

6. In the combination of claim l, the feature that there are severalgroups of cable guides with each group mounted on a mounting member as aunit for movement with said mounting member relativelyto other groups ofcable guides mounted on other mounting members, and cam means throughwhich said piston moves said mounting members to move said groups ofguide members away from one another.

7. In the combination of claim 6, the feature that each of said cableguides is a pulley individually mounted for rotation on one of saidmounting members while moving bodily with said mounting member.

8. In the combination of claim 6, the feature that each of said mountingmembers is so moved by said piston through cam and roller mechanism.

9. In the combination of claim l, the feature that a group of said cableguides is mounted on each of a plurality of mounting members, and thatthe endwise movement of the piston moves said mounting members radiallyof the axis of said piston.

10. In the combination of claim 9, the feature that each of saidmounting members is in the form of a beam having a roller and camconnection at one end with the casing of said hoist and a similarconnection at its other end with said piston.

11. In the combination of claim 9, the feature that said ram cylinderand piston are in aV casing in which said mounting members are alsomounted and that said piston is formed with a cam surface coacting witha part of each of said mounting members, a circular skirt on one end ofsaid piston whereby said piston is movably mounted in said cylinder, aseries of arms on said piston extending longitudinally from said skirt,outwardly of the ram cylinder, and internal surfaces formed on thecasing of said hoist against which said arms ride.

12. In the combination of claim 9, the feature that said piston isformed with a circular skirt slidable in the ram cylinder, and a seriesof circumferentially angularly spaced cam surfaces, each extending fromsaid skirt angularly toward the axis of the piston, said cam surfaceseffecting the movement of the mounting members.

13. In the combination of claim 12, the feature that said ram cylinderand piston are in a casing in which said mounting members are alsomounted, and that said piston has a series of arms positionedcircumferentially angularly between said cam surfaces and extendingoutwardlyl of the ram cylinder to lie against the internal surface ofthe casing of said hoist for guiding said piston.

14. In the combination of claim l, the feature that said piston isformed with a circular skirt whereby said piston is mounted in said ramcylinder, and a series of circumferentially angularly spaced camsurfaces each extending from said skirt angularly toward the axis of thepiston, said cam surfaces effecting the movements of said guides.

15. In the combination of claim 14, the feature that said ram cylinderand piston together with said guides are within a casing, and that saidpiston has a series of arms positioned circumferentially angularlybetween said cam surfaces and extending outwardly of the ram cylinder tolie against the internal surface of the casing of said hoist for guidingsaid piston.

16. In the combination of claim 1, the feature that one end of saidcable is fixed to said hoist while the other end extends from one ofsaid guide surfaces to a load, whereby the lengthening of that portionof the cable in said helical path effects lifting of said cable.

17. In the combination of claim l, the feature that said ram pistonmoves within the space outlined by said guide surfaces and effectsmovement of said guides radially.

18. In the combination of claim l, the feature that said ram cylinderand guides are within a casing with one end of said cable passing out ofsaid casing for lifting a load, said piston having a skirt whereby itslides in said ram cylinder, the axis of said cylinder and piston beingin alignment with the axis of said helical path, a series ofcircumferentially angularly spaced cam surfaces formed on portions ofsaid piston extending from said skirt for moving said guides as saidpiston moves axially in said cylinder, a series of arms alsocircumferentially angularly spaced extending from said skirt and lyingoutwardly of said cylinder, and portions of said casing for guiding saidarms and thereby effectively reinforcing said piston.

19. In the combination of claim 1, the feature that there are twopistons in said ram cylinder sliding in opposed directions,

and means whereby eac-h of said pistons acts against mounting' memberson which said guides are mounted to move said guides.

1. In a hoist of the class described, a load cable, a series of spacedcable guides movably mounted on said hoist and having guide surfacesover which said cable is applied, said guide surfaces definingtherebetween a helical path for said cable, a ram cylinder on said hoistpositioned with its piston moving in an axis traversing the spacedefined by said helical path and parallel to the longitudinal axis ofsaid helical path, and means whereby said piston moves at least certainof said guides transversely of the axis of said piston and said helicalpath to move said guides in directions away from one another whereby toeffect a lengthening of said helical path and increased winding of saidcable about said guides.
 2. In the combination of claim 1, the featurethat said cable guides are mounted to rotate in axes that are parallelto the axis of said ram piston.
 3. In the combination of claim 2, thefeature that said cable guides comprise a series of independentlyrotating grooved pulleys.
 4. In the combination of claim 3, the featureof cam means through which sliding movement of said piston moves saidgrooved pulleys.
 5. In the combination of claim 1, the feature that saidram piston moves in the axis of said helical path, and cam meansactuated by said piston for moving said guides radially of said axis. 6.In the combination of claim 1, the feature that there are several groupsof cable guides with each group mounted on a mounting member as a unitfor movement with said mounting member relatively to other groups ofcable guides mounted on other mounting members, and cam means throughwhich said piston moves said mounting members to move said groups ofguide members away from one another.
 7. In the combination of claim 6,the feature that each of said cable guides is a pulley individuallymounted for rotation on one of said mounting members while moving bodilywith said mounting member.
 8. In the combination of claim 6, the featurethat each of said mounting members is so moved by said piston throughcam and roller mechanism.
 9. In the combination of claim 1, the featurethat a group of said cable guides is mounted on each of a plurality ofmounting members, and that the endwise movement of the piston moves saidmounting members radially of the axis of said piston.
 10. In thecombination of claim 9, the feature that each of said mounting membersis in the form of a beam having a roller and cam connection at one endwith the casing of said hoist and a similar connection at its other endwith said piston.
 11. In the combination of claim 9, the feature thatsaid ram cylinder and piston are in a casing in which said mountingmembers are also mounted and that said piston is formed with a camsurface coacting with a part of each of said mounting members, acircular skirt on one end of said piston whereby said piston is movablymounted in said cylinder, a series of arms on said piston extendinglongitudinally from said skirt outwardly of the ram cylinder, andinternal surfaces formed on the casing of said hoist against which saidarms ride.
 12. In the combination of claim 9, the feature that saidpiston is formed with a circular skirt slidable in the ram cylinder, anda series of circumferentially angularly spaced cam surfaces, eachextending from said skirt angularly toward the axis of the piston, saidcam surfaces effecting the movement of the mounting members.
 13. In thecombination of claim 12, the feature that said ram cylinder and pistonare in a casing in which said mounting members are also mounted, andthat saiD piston has a series of arms positioned circumferentiallyangularly between said cam surfaces and extending outwardly of the ramcylinder to lie against the internal surface of the casing of said hoistfor guiding said piston.
 14. In the combination of claim 1, the featurethat said piston is formed with a circular skirt whereby said piston ismounted in said ram cylinder, and a series of circumferentiallyangularly spaced cam surfaces each extending from said skirt angularlytoward the axis of the piston, said cam surfaces effecting the movementsof said guides.
 15. In the combination of claim 14, the feature thatsaid ram cylinder and piston together with said guides are within acasing, and that said piston has a series of arms positionedcircumferentially angularly between said cam surfaces and extendingoutwardly of the ram cylinder to lie against the internal surface of thecasing of said hoist for guiding said piston.
 16. In the combination ofclaim 1, the feature that one end of said cable is fixed to said hoistwhile the other end extends from one of said guide surfaces to a load,whereby the lengthening of that portion of the cable in said helicalpath effects lifting of said cable.
 17. In the combination of claim 1,the feature that said ram piston moves within the space outlined by saidguide surfaces and effects movement of said guides radially.
 18. In thecombination of claim 1, the feature that said ram cylinder and guidesare within a casing with one end of said cable passing out of saidcasing for lifting a load, said piston having a skirt whereby it slidesin said ram cylinder, the axis of said cylinder and piston being inalignment with the axis of said helical path, a series ofcircumferentially angularly spaced cam surfaces formed on portions ofsaid piston extending from said skirt for moving said guides as saidpiston moves axially in said cylinder, a series of arms alsocircumferentially angularly spaced extending from said skirt and lyingoutwardly of said cylinder, and portions of said casing for guiding saidarms and thereby effectively reinforcing said piston.
 19. In thecombination of claim 1, the feature that there are two pistons in saidram cylinder sliding in opposed directions, and means whereby each ofsaid pistons acts against mounting members on which said guides aremounted to move said guides.